This application is aimed at the detailed specification of laryngeal function in normal phonation and speech. The role of intrinsic and extrinsic laryngeal muscles, and subglottal pressure will be considered in controlling fundamental frequency and laryngeal structure in normal speech production. The same factors will be considered for laryngeal activity in stuttering. For both normal and abnormal phonation, measures will be made of subglottal presure, EMG, and larynx height and configuration.